Question

RabbitMQ 3.5现在supports message priority; 但是，我无法建立一个有效的例子。我把我的代码放在下面。它包括我期望的输出和实际的输出。我会对更多文档和/或工作示例感兴趣。

所以我的问题很简单：如何在Rabbit 3.5.0.0中使用消息优先级？

出版商：

using System;
using RabbitMQ.Client;
using System.Text;
using System.Collections.Generic;

class Publisher
{

    public static void Main()
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
        using (var connection = factory.CreateConnection())
        {
            using (var channel = connection.CreateModel())
            {
                IDictionary <String , Object> args = new Dictionary<String,Object>() ;
                args.Add(" x-max-priority ", 10);
                channel.QueueDeclare("task_queue1", true, false, true, args);

                for (int i = 1 ; i<=10; i++ )
                {
                    var message = "Message";
                    var body = Encoding.UTF8.GetBytes(message + " " + i);
                    var properties = channel.CreateBasicProperties();
                    properties.SetPersistent(true);
                    properties.Priority = Convert.ToByte(i);
                    channel.BasicPublish("", "task_queue1", properties, body);
                }
            }
        }
    }
}

消费者：

using System;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using System.Text;
using System.Threading;
using System.Collections.Generic;

namespace Consumer
{ 
    class Worker
    {
        public static void Main()
        {
            var factory = new ConnectionFactory() { HostName = "localhost" };
            using (var connection = factory.CreateConnection())
            {
                using (var channel = connection.CreateModel())
                {
                    IDictionary<String, Object> args = new Dictionary<String, Object>();                      
                    channel.BasicQos(0, 1, false);
                    var consumer = new QueueingBasicConsumer(channel);
                    IDictionary<string, object> consumerArgs = new Dictionary<string, object>();
                    channel.BasicConsume( "task_queue1", false, "", args, consumer);
                    Console.WriteLine(" [*] Waiting for messages. " +
                                      "To exit press CTRL+C");
                    while (true)
                    {
                        var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
                        var body = ea.Body;
                        var message = Encoding.UTF8.GetString(body);
                        Console.WriteLine(" [x] Received {0}", message);
                        channel.BasicAck(ea.DeliveryTag, false);
                    }
                }
            }
        }
    }
}

实际输出：

[*] Waiting for messages. To exit press CTRL+C
[x] Received Message 1
[x] Received Message 2
[x] Received Message 3
[x] Received Message 4
[x] Received Message 5
[x] Received Message 6
[x] Received Message 7
[x] Received Message 8
[x] Received Message 9
[x] Received Message 10

预期产出：

[*] Waiting for messages. To exit press CTRL+C
[x] Received Message 10
[x] Received Message 9
[x] Received Message 8
[x] Received Message 7
[x] Received Message 6
[x] Received Message 5
[x] Received Message 4
[x] Received Message 3
[x] Received Message 2
[x] Received Message 1

更新＃1。我在Java here中找到了一个例子。然而，它是Rabbit 3.4.x.x.添加到3.5中的插入。我能看到的唯一区别是它们将优先级表示为int而我的是一个字节。但我觉得那是一个红鲱鱼。我在这里有点不知所措。

Answer 1

我解决了。这是一个愚蠢的错误。我写道：

args.Add(" x-max-priority ", 10);

应该是

args.Add("x-max-priority", 10);

我会放弃这一点，以便其他人可以在C＃中找到Rabbitmq 3.5优先级队列的工作示例。

Answer 2

Node JS中类似的RabbitMq优先级队列实现

安装amqplib

为了测试，我们需要安装amqplib

npm install amqplib

Publisher（send.js）

#!/usr/bin/env node

var amqp = require('amqplib/callback_api');

function bail(err, conn) {
  console.error(err);
  if (conn) conn.close(function() { process.exit(1); });
}

function on_connect(err, conn) {
  if (err !== null) return bail(err);

  // name of queue
  var q = 'hello';
  var msg = 'Hello World!';
  var priorityValue = 0;

  function on_channel_open(err, ch) {
    if (err !== null) return bail(err, conn);
    // maxPriority : max priority value supported by queue
    ch.assertQueue(q, {durable: false, maxPriority: 10}, function(err, ok) {
      if (err !== null) return bail(err, conn);

      for(var index=1; index<=100; index++) {
             priorityValue = Math.floor((Math.random() * 10));
             msg = 'Hello World!' + ' ' + index + ' ' + priorityValue;
             ch.publish('', q, new Buffer(msg), {priority: priorityValue});
             console.log(" [x] Sent '%s'", msg);
      }

      ch.close(function() { conn.close(); });
    });
  }

  conn.createChannel(on_channel_open);
}

amqp.connect(on_connect);

订阅者（receive.js）

#!/usr/bin/env node

var amqp = require('amqplib/callback_api');

function bail(err, conn) {
  console.error(err);
  if (conn) conn.close(function() { process.exit(1); });
}

function on_connect(err, conn) {
  if (err !== null) return bail(err);
  process.once('SIGINT', function() { conn.close(); });

  var q = 'hello';

  function on_channel_open(err, ch) {
    ch.assertQueue(q, {durable: false, maxPriority: 10}, function(err, ok) {
      if (err !== null) return bail(err, conn);
      ch.consume(q, function(msg) { // message callback
        console.log(" [x] Received '%s'", msg.content.toString());
      }, {noAck: true}, function(_consumeOk) { // consume callback
        console.log(' [*] Waiting for messages. To exit press CTRL+C');
      });
    });
  }

  conn.createChannel(on_channel_open);
}

amqp.connect(on_connect);

执行命令

node send.js

它将创建一个名为“hello”的队列，并使用默认的AMQP交换将其填充为“1000”样本消息。

node receive.js

它将作为消费者订阅在队列中等待的消息。

Answer 3

另一种可能性（对于未来的搜索者）

＆＃34; Push＆＃34;消息传递方法似乎并不尊重优先权。

http://rabbitmq.docs.pivotal.io/35/rabbit-web-docs/dotnet-api-guide.html.html

下面的是来自上述网址的引用。我把重要的部分加粗了。

按订阅检索邮件（＆＃34;推送API＆＃34;）

接收消息的另一种方法是使用IBasicConsumer接口设置订阅。 消息将在到达时自动传递，而不是必须主动请求。实现消费者的一种方法是使用便利类EventingBasicConsumer，它将交付和其他消费者生命周期事件作为C＃发送事件：

var consumer = new EventingBasicConsumer(channel); consumer.Received += (ch, ea) => { var body = ea.Body; // ... process the message ch.BasicAck(ea.DeliveryTag, false); }; String consumerTag = channel.BasicConsume(queueName, false, consumer);

通过更改为＆＃34; pull＆＃34;方法，优先权似乎得到尊重。但是，在下面的引用（来自上面的同一个网址），看起来有一个权衡（我加粗）

获取个人消息（＆＃34;拉动API＆＃34;）要检索单个邮件，请使用IModel.BasicGet。返回的值是BasicGetResult的一个实例，可以从中提取标题信息（属性）和消息正文：

bool noAck = false; BasicGetResult result = channel.BasicGet(queueName, noAck); if (result == null) { // No message available at this time. } else { IBasicProperties props = result.BasicProperties; byte[] body = result.Body; ...

由于上面的noAck = false，您还必须调用IModel.BasicAck以确认您已成功接收并处理了该消息：

... // acknowledge receipt of the message channel.BasicAck(result.DeliveryTag, false); }

请注意，使用此API提取邮件的效率相对较低。 如果您更喜欢RabbitMQ将邮件推送到客户端，请参阅下一节的

（在这种情况下，＆＃34; next＆＃34;部分将带您进入本文顶部的＆＃34; push＆＃34;方法）

RabbitMQ 3.5和消息优先级

3 个答案: